PC powers down intermittently - help

Asus P4c800 motherboard
December 28, 2009 at 06:07:31
Specs: Windows XP
This is a problem that I have had for two years that happens intermittently and is VERY annoying. The PC is custom built and 6 years old.

When accessing disk intensive applications the PC switches itself off - completely as if someone has pulled the plug. Sometimes the PC is just playing music and switches itself off.

I have carried out the following-

replaced the video card
replaced the PSU
replaced the RAM
replaced the motherboard and processor
reinstalled the Operating System
changed the power plugs
changed the internal data ribbons
changed the hard disk
cleaned out all the dust
I have run memtest, everest home edition and other recommended programs all to no avail. The only thing that is still the same is the case unit. I have unplugged all power supplies apart from power on, taken out all circuit boards and still get this problem.

There can't be anything left to try.

One thing that is good is that I can now reproduce the problem consistently - when I use itunes to scan a CD and replace tunes in the database with the rescanned ones the power out problem happens. In some ways I am happy about this as I can consistently troubleshoot the issue ( I have changed CD drives as well to no avail)

Does anyone have a magic solution?

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December 28, 2009 at 06:33:08
You generically listed which parts you changed out, but it would help if you were more specific. Start by listing your current system specs in detail, then list what you swapped from & to. I suspect the power supply so when you list that, be VERY specific...not just "350W to 500W", that's useless. We'd need to know the make/model of each unit, the wattage rating, plus the amperage ratings for the +3.3v, +5v & +12v rails.

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December 28, 2009 at 08:36:13
thanks for the quick reply - system details are

Asus P4C800 motherboard (http://www.ece.umd.edu/courses/enee759h.S2003/references/e1286_p4c800.pdf)
(Replaced in 2007 with identical motherboard sourced off ebay)
CPU pentium 4 2.4 GHz ( replaced 2007)
BIOS is AMi build 08.00.09 14 oct 2004
Jeanster 405w PSU (Installed in 2008)
1GB RAM ( 2x 512MB) replaced in 2009 with 2x 1GB Hynix DDR 400Mhz
Seagate IDE barracude 80 Gbyte hard drive replaced with 200GB SATA ST3120026AS ( installed last few days)
SATA and IDE data cables replaced on motherboard. All unnecessary power sockets have had their cables removed for testing ( eg CPU fan power, HD LED, etc)

temperatures and voltages are;

CPU 32 C
MB 18
vcore volt 1.55
3.3v 3.296
5v 4.9999
12v 12.099v

If I boot from CD and only have the CD running then the machine can brownout while loading "linux gparted". This behaviour is inconsistent though and the only consistent behaviour is the itunes method. But it does suggest to me that it's not the operating system.

Note that the case has two power switches - one on the PSU and one at the front. If I turn off the PSU one the BIOS loses the date settings and gives me " a new CPU has been installed" message.

I'm thinking there might be some BIOS setting that is causing this?

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December 28, 2009 at 11:57:17
"If I turn off the PSU one the BIOS loses the date settings and gives me " a new CPU has been installed" message"

Sounds like the CMOS battery is dead. They're about $3 US.

"All unnecessary power sockets have had their cables removed for testing ( eg CPU fan power, HD LED, etc)"

CPU cooling fan too?

"Jeanster 405w PSU"

Do you mean Jeantech? Like THIS one? When it comes to PSUs, you get what you pay for:


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Related Solutions

December 28, 2009 at 12:48:46
cheers. Yeah, I need a new CMOS.

I turned off the CPU fan temporarily until I could see that it was not causing a problem. It's back on now

Jeantech is right. Exactly as the link says ( although I paid a lot more at PC World). But to run one hard disk and CD ROM I thought that should be okay?

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December 30, 2009 at 06:47:43
now put my pc back together ( and have new CMOS)

Just after booting it switches itself off sometimes, still switches itself off every time at the itunes import tunes task when overwriting other tunes. I'm reluctant to spend more money on this system considering what I have replaced so far - the 500W PSU's seem expensive...

Is there no other testing software that could be run?

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January 6, 2010 at 11:59:47
Now have bought and installed 750w power supply - problem worse than ever and windows does not boot nor does booting from the CD work. The PC powers down. Safe boot and recovery console all give same issues where PC switches off. This is driving me crazy. Any further ideas?

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